The purpose of the implant is to reinforce certain parts of the skeleton by use of strategically placed bone attachment devices. In some cases, these devices may support alignment support rods placed bilateral along the vertebrae as well as cross-link plates that bridge the spine.
Conventionally, pedicle screws are use to attach the implants to the bone. However, there are instances in which it is not desirable or possible to use screws. Other attachment devices, such as hooks, may be used when it is not desirable to penetrate the bone. Usually, these hooks or screws are rigid one piece constructions. Due to the various anomalies of the skeleton, occurring naturally or by trauma, it is difficult to place a series of attachments in such a manner that a uniformly shaped plate or rod can be connected without creating additional stress on the skeleton.
Further, in the case of the hooks there is the possibility of movement of the attachment point.